Technical Field
The present disclosure relates to an imaging optical system and an image capturing apparatus, and more particularly, to an imaging optical system and an image capturing apparatus applicable to electronic devices.
Description of Related Art
As personal electronic products nowadays are becoming more and more compact, the internal components of the electronic products are also required to be smaller than before, resulting in an increasing demand for compact imaging optical systems. In addition to the demand of miniaturization, the reduction of the pixel size of image sensors in the advanced semiconductor manufacturing technologies has enabled imaging lenses to evolve toward the field of higher megapixels. Meanwhile, the popularity of smartphones and tablet personal computers boosts the need for compact imaging optical systems featuring high image quality.
A conventional imaging optical system comprising four lens elements typically comprises a fourth lens element having a concave image-side surface. Although such a configuration is favorable for reducing the back focal length of the imaging optical system, it is not favorable for suppressing the incident angle of the light projecting onto an image sensor. In addition, for a telephoto optical system that has a smaller field of view, the conventional configuration as described above may have its drawback, as it would be hard to obtain a balance between a favorable manufacturing process and an appropriate sensitivity of the system.
Although the configuration of a conventional imaging optical system comprising four lens elements is advantageous in keeping a compact size, image quality of such a system still needs improvements. Therefore, a need exists in the art for an imaging optical system that features a compact design and high image quality.